The objectives of this project are: (a) to establish sensory and pain thresholds to tooth pulp electrical stimulation in myofascial pain dysfunction (MPD) patients; (b) to relate sub-sensory, sensory and pain producing stimuli of the tooth pulp to the masseteric exteroceptive reflex in MPD patients, by means of electromyographic (EMG) recordings; (c) to compare the exteroceptive to the proprioceptive suppression of ongoing EMG activity in the masseters of these patients. In all these cases comparison between MPD patients to normal subjects will enable a better understanding of the MPD syndrome pain and dysfunction mechanisms, and the gain of insight into possible protective mechanisms of the exteroceptive reflex.